1. Field of the Invention
This invention relates to a wide-angle zoom lens and a photographing apparatus using this zoom lens.
2. Description of Related Art
A zoom lens constructed with two lens units which have a positive refracting power and a negative refracting power, in this order from the object side, has been widely used because a small number of lens components is required and its arrangement is simple.
Conventional wide-angle zoom lenses of this type, in which the total field angle at a wide-angle position is 70xc2x0 or more, are known by U.S. Pat. Nos. 5,162,947, 5,353,163, 5,483,380, and 5,633,760.
Since each of these zoom lenses contains a cemented lens element in one lens unit and an independent fabrication process for cementing lenses is required, working time and period required for fabrication are increased accordingly. Furthermore, the zoom lens has a variable-magnification ratio of 2.1 or less and it is difficult to obtain a high magnification. In addition, distortion at the wide-angle position is positive, and thus considerable distortion is produced on the periphery of an image.
A zoom lens of the type that a variable-magnification ratio is 2.5 or more and the cemented lens element is not contained in the lens unit is disclosed in Japanese Patent Preliminary Publication No. Hei 11-84236. However, in order to correct aberration with a small number of lens components, it is necessary to use ED glass which is difficult in workability. Moreover, since a plurality of aspherical surfaces must be used, the zoom lens has the demerit that it is not suitable for mass production.
It is, therefore, an object of the present invention to provide a wide-angle zoom lens which includes a first lens unit with a positive refracting power and a second lens unit with a negative refracting power, has a total field angle of at least 70xc2x0 at the wide-angle position and a variable-magnification ratio of 2.5 or more, is constructed with single lens elements, and is simple in arrangement, and a photographing apparatus using this zoom lens.
In order to achieve the above object, the wide-angle zoom lens according to the present invention includes, in order from the object side, the first lens unit with a positive refracting power and the second lens unit with a negative refracting power so that a space between these lens units is changed and thereby the magnification of the zoom lens can be varied. The first lens unit is constructed with a first lens component which is only one negative lens component in the first lens unit, placed at the most object-side position, and at least three positive lens components arranged on the image side of the first lens component to provide air spaces between them. Each of lens components constituting the first lens unit is constructed with a single lens element.
In the wide-angle zoom lens according to the present invention, the first lens unit satisfies the following condition:
0.5 less than |f1L/f1G| less than 1xe2x80x83xe2x80x83(1) 
where f1L is the focal length of the first lens component constructed with a single negative lens component and f1G is the focal length of the first lens unit.
The photographing apparatus using the wide-angle zoom lens according to the present invention employs the wide-angle lens mentioned above as an objective lens.
This and other objects as well as features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.